This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Histone post-translational modifications play a pivotal role in gene regulation, chromatin packaging and cellular differentiation. The histone deacetylase (HDACs) mSin3A complex is involved in transcriptional repression and contains multiple subunits that have been implicated in growth control, including HDAC 1 and 2, the Breast Suppressor of Metastasis 1 proteins (BRMS1 and BRMS1L1), and the p33/ING1 tumor suppressor proteins. However, our preliminary data suggest that mSin3A complex may be compositionally diverse in different cell types and under different growth conditions. Isolation and characterization of different Sin3A subunits is essential for elucidating the role of the various mSin3A complexes. Using mass spectroscopy, we aim to identify associated proteins, and determine how they interact with other subunits. These data will guide functional studies to determine effects on cell proliferation, gene expression and genomic stability.